Coil for electrical transformers



J. ROOTHAAN IApril '28, 1925. l 1,535,859

COIL FOR ELECTRICAL TRANSFORMERS Filed Feb. s, 1922 s sheets-sheet 1 QN wl) IIIIIIIIHIHII l "Hl Q """IIIHIIIIIII"Hllllllllll I "um,

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J.v ROOTHAAN COIL FOR ELECTRICAL TRANSFORMERS Filed Feb'. 8. 1922 3 She'ets-Sheet 3 til"'V'HIW'I m il .nl wl Ik! lul lm um kwh I il Ilm UAH Patented Apr. 28, 1925.

UNITED STATES JAN ROOTHAAN, 0F HAYES, ENGLAND.

COIL FOR ELECTRICAL TRANSFORlvTERS.

Application led 'February 8, 1922. Serial No. 534,888.

To @ZZ i12/tom t may concern.'

Be it known that I, JAN Roo'rHaaN, a subject of the Queen of the Netherlands, residing` at Hayes, Middlesex, England, have invented lmproif'ements in or Relating to Coils for Electrical Transformers, of which the following is a specification.

This invention relates to improvements in the construction of coils for electrical transformers, particularly those designed to be used in high voltage transformers.

The solid insulation materiai used between the turns of a. transformer coil or winding, usually consists of a composite material, the basis of which is cotton, flax, paper silk or like fibrous material, impregnated or treated with varnish, oils and the like. Such material as a rule is more or less hygroscopic, shrinks When in use, is a bad conductor of heat and is easily damaged by abrasion and otherwise. Moreover, when several layers of such materialy are Wound between and over the turns of conductor, the

insulation cannot be considered homogeneous; and owing to the composite nature of such material being of varying specific inductive capacities, the dielectric strength of such insulation is more or less an unkoWn quantity.

The object of the present invention is to use for the insulation of transformer coils apart from the oil in which the transformer may be immersed when in use, solid insulating material free from the objectional features above referred to.

For this purpose, there is used according to the present invention, for insulatingl` the turns of the conductor forming a transformer coil1 homogeneous insulating material of the kind commercially known as bakelite, formite, formalite and the like or of pure mica Which is practically non-hygroscopic, heat resisting, mechanicaliy strong, very refractory; does not Warp or shrink and is an excellent insulator. Of such insulation materials, it is preferred to use one having the same or substantially the same specific inductive capacity as the oil in which the transformer embodying such a. coil is immersed when in use.

In the construction of a transformer coii embodying such insulation material, according to the present invention, the coil is formed of bare conductor of circular, rectangular or other suitable cross section, the

turns of which are mainly insulated from each other by air during the construction of the coil and afterwards by tne oil in which the transformer containing the coil may be immersed when in use, solid insulation material being used in the form of suitably shaped separators, binders and distance pieces, for holding` the turns together and taking up mechanical stresses. The separators, binders and distance pieces should, in order to obtain the best results, be shaped in such a manner as to conform with the linesl of force of the electrostatic field produced adjacent thereto when the coil is in use.

Si. transformer coil thus constructed possesscs many practical advantages. Thus, when the coil is in use, not only the oil in Which it is submerged can be considered as homogeneous (which is very important from an insulating point of View), but also, the solid insulating material used as separators, binders and distance pieces. The latter ma terial is not liable to absorb moisture. Due to this and to the fact that when the soli@l insulation material has a different specific inductive capacity to that of the oil, the separators, binders and distance pieces can be shaped so as to conform to the lines of force of the electrostatic field adjacent thereto, so that the-break-down voltage between adjacent turns of conductor or between the conductor and nearest earth, can be accurately determined. which 1s not possible with the usual methods of insulation involving` the use of fibrous material.

rlfhe cooling of the coil also is excellent. Tf due to outside disturbances, the oil insulation between any neighbouring turns of conductor be pierced, the oil insulation will immediately be restored whereas with the usual method of insulation, the damage is permanent. Also, the grading of the insulation of reinforced coils can be made theoretically correct and there is no shrinkage of the solid insulation material used. Furthermore, no moisture can be absorbed by the insulating' material when the transformer is taken out of the oil tank. Consequently, drying out, a very important and difiicult matter With transformer coils having any fibrous insulation, is reduced to a Very sinrple and easily carried operation.

Transformer coils embodyingthe invention can be constructed in various Ways to obtain lthe advantages of the invention.

In the accompanyingl illustrative drawings, Fig. 1 shows in side elevation. Fig. 2 in cross section 4on the line 2 2 of Fig. 1 and Fig. 3 in plan, part of a transformer coil, according to the invention and how itA is constructed, the coil being shown onva former. Figs. etto 7 are'deta'il 'views7 Figs. t and 41a being respectively a side View and end view of a radial separator, Figs. 5 and 5 a face view and edge view respectively of a distance piece, Figs. 6 and 6? views atright angles to one another of a radial binder; and Figs. 7 and 7a a facev and edge view respectively of connecting means between the adjacent ends of two coils-of conductor. Figs. 8, 9 and 10- a-re respectively a side eleva-tion, plan and crossl section of partof a former for use in building up coils according to the invention. Figs. 11 and 12 are respectively a plan and side elevation of part cfa modified construction oi' coil. Fig. 13 is a detail view of two adjacent radial binders. Fig. 14 shows in cross section, vpart ot amodified construction of coil. Figs. 15

andlG show respectively in plan and cross section, part of a still further modified construction of coil, whilst Fig. 17 shows separately, one of the insulating distance pieces used therein.

In the construction of transformer coil shown in Figs. 1, 2 and 3, there are two sets L and 0 ofl turns .ory convolutions (hereinafter called convolutions) `formed of bare strip coppe-r, arranged in parallel planes and separated `from each other laterally by a` number of suitably spaced radial separators Y' c (Figs. and et) formed of solid insulating material of the lrind herein referred to, for example balrelite or formalite, each such separator being Vin the'forin of' a rod ofr square or rectangular cross section. and hav- `ing a head c1 atits inner end adjacent to Athe inner periphery ofthe two sets a and b of convolutions. Between the successive convolutions of copperstrip in each set a and b thereof, and in proximity to the radial separators c, are distance pieces CZ (Figs. 5 and 5a) consisting of flat rectangular pieces of insulating `material Vof the kind referred to. At the outer sides of each of the two sets of convolutions a, and lil are a nuinberof radialbinders e ('Figs. 6 and Ga) formed of insulating material ot the kind referred'to,

ai-ranged, it may be, and as shown, in the saine transverse planes 'as the radial separatois c and each provided at its inner and outer ends with laterally extending projections or lugs el., c2 respectively adapted to be forced over the complete set a or 7) of convolutionsof strip conductor constituting the adjacent coil so as tov bind the turns of conductor and interposed distance'pieces (Z firmly together. Each binder e may be of square l or rectangular shape in cross section. Each Lacasse of its oppositeedges with square or rec-'- tangularl shaped notches Z1 to fit the adjacent radial separator c and binder e and thereby be. held securely in position. r1`he end portions L1-and o1 (Fig. 7) of the two sets of convolutions a and o constituting a pair of coils are suitably formed to enable them to be connected together in series to 'form a unit and to adjacent sets of similarly constructed coils forming adjacentv units. Such connection may be effected by the aid of a short strip of copper f (Figs. 7 and 7a) riveted to the adjacent ends of the coiled strips and having a .transversely arranged expansion Vbend f1 therein.

For constructing such a pair of coils, there may advantageously be used a former (Figs. 2, 8, 9 and 10) consisting of a central hub composed of two nietal rings g, g1 arranged side by side and dctachably connected togethenas by set screws t, and a series of U shaped inet-al guide bars 7l secured to the youter sides of the hub,v as by set screws y'.

The combined rings are formed at the outer periphery and at their innerv sides with recesses 7c to torni slots in which theinner enlarged ends c2 ofthe radial separators 0 can gether by a strip of copper, as shown in Figs. 7, 7, be fixed preparatory to winding the strips into Acoil form which is done by winding them between the U shaped guide bars 2' and the radial separators o (Figs. 1 and 2) the fiat distance pieces cl being placed in position as the winding proceeds. lVhen the winding is finished, the binders e are forced into place laterally to hold the two sets a andy b of convolutions of conductor firmly together. .The two rings g, g1 with guide bars z' are then separated vfrom each other and the complete set of coils removed. In the modified construction sho-wn in Figs. 11 and 12. the convolutions of bare conductor in each set al and 'b thereof are separated at intervals by fiat distance pieces CZ of insulating material of the kind referred to, formed at one side only with a notch Z1 of dove tailshape through which extends a radial separator c of corresponding shape in cross section. In such a case the distance pieces f/Z may, as sho-wn, extend beyond one side only of the corresponding set of convolutions and the corresponding radial separators omay, as shown. extend slightly beyond the distance pieces so as to bear against any adjacent set of convolutions.

lllhen two or more such pairs of coils a and Z) are to be assembled sideways of one llO another, the binders e on one side of one pair of coils may each be formed with a radial rib e3, as shoivn in Fig. 13, and those on the other side be each formed with a corresponding radial recess 6*, so that the ribs on the binders on one side of one set or pair of coils a and o can enter recesses in the binders of an adjacent set orv pair of coils, for the purpose of easily positioning the sets of co-ils. v

The edges of the copper strips may be of curved shape, as also may be the edges of the distant pieces, radial separators and binders for the purpose hereinbefore mentioned.

ln the construction of the double coil shown in Fig. ld, the adjacent convolutions of each of the coils a and o formed of copper strips having rounded edges, are separated by distance pieces d of insulating material recessed on each side to iit the adjacent sides and edges of the convolutions of conductor and having rounded edges extending Jfrom the edges of the coiwolutions so as to provide for uniform electro-static tields between the turns at all parts thereof. The radial separators c between adjaccntcoils a, and Z) and the binders e may be shaped to fit the rounded edge portions of the convolutions and distance pieces CZ or not as may be desired. The said parts are shown as fitting one another.

ln the case of coils formed of convolutions of copper conductor of circular section, as shoivn in Figs. l5, 16 and 17, the distance pieces l may, as shown, have rounded inner and outer edges Z2 With intermediate oppositely arranged concave recesses (Z5 to receive the convolutions of conductor. In this case the radial separators c are displaced angularly with reference to the dis` tance pieces d and may be formed on opposite sides with concave recesses c3 to receive the convolutions of adjacent coils. The binders, notshoivn, may also be similarly recessed on one side to receive the turns of the adjacent coil.

The details of construction of electrical transformers embodying the invention, can be variously modified.

lVhat I claim is l. A transformer coil comprising adjacent sets of convolutions of bare conductor, radial separators adapted to space the sets of convolutions apart, distance pieces, each consisting of a small plate, interposed between successive convolutions of the same set to space them apart., and radial binders applied to each set of convolutions after the Winding there f is completed, the separators, distance pieces and .binders being separate members all formed of homogeneous insulating material and being arranged at intervals around the convolutions of conductor in such a manner that the convolutions are mainly insulated from each other by air previous to immersion in oil.

2. A transformer coil comprising1 adjacent sets of convolutions of bare conductor, radial separators adapted to space the sets of convolutions apart, distance pieces, each consisting' of a small plate, interposed bet-iveen successive convolutions of the same setto space them apart, one edge of each distance piece extending laterally beyond the edge of the convolutions, the said edge of the distance piece being so shaped as to be adapted to interlock With a radial separator, and radial binders applied to each set of convolutions after the winding thereof is completed, the separators, distance pieces and binders being separate members. all formed of homogeneous insulating material and being arranged at intervals around the convolutions of conductor in such a manner that the convolutions are mainly insulated from each other by air previous to immersion in oil.

. A transtormer coil comprising adjacent sets of convolutions ot' bare conductor, radial separators adapted to space the sets of convolutions apart, distance pieces, each consisting of a small plate, interposed betiveen successive convolutions of the same set to space them apart, one edge of each distance piece extendinglaterally beyond the edge of the convolutions, and radial binders applied to each set of convolutions after the Winding thereof is completed, the protruding edge of each distance piece being so shaped as to be adapted to interlock with an adjacent radial binder, the separators, distance pieces and binders being separate members all formed of homogeneous insulating material and being arranged at intervals around the convolutions of conductor in such a manner that the convolutions are mainly insulated from each other by air previous to immersion in oil.

il. A transformer coil comprising adjacent sets of convolutions of bare conductor, radial separators adapted to space the sets of convolutions apart, distance pieces, each consisting of a small plate interposed between successive convolutions of the same set to space them apart, and radial binders applied to each set of convolutions after the Winding thereof is completed, the distance pieces betiveen adjacent convolutions of bare conductor being recessed at opposite sides to form recesses for the reception of the convolutions, and the separators, distance pieces and binders being separate members all formed of homogeneous insulating` material and being arranged at intervals around the eonvolutions of conductor in such a manner that the convolutions are mainly insulated from each other by air previous to immersion in oil,

5. transformer coil comprising adjacent sets of convolutions of bare conductor geneous insulating niaterial arranged in:

tervals around the convolutions or' conductor in such a inanner that the eonvolutions vare mainly insulated 'freni one anotherby air previousto immersion in oil, and the edges of the bare conductor forming the sets of convolutions and the adjacent edge portions of the distance pieces, separators and binders .being shaped to contorni with the lines of force of ther electrostatic field set up When the coil is in use. v

V6. A transformer coil constructed according to claim l, the binders at opposite sides ot' a coil having two sets of `convolutions of the conductor adapted to interlock with the binders ot one or more adjacent similarly constructed coils, substantially as *described spaced binders at the outer sides of the connected sets of convolutions7 each binder being` adapted at its ends to clanipthe corresponding set of convolutions and interposed distance pieces. iirnily together, the distance pieces, radial separators, and binders being tornied of hard7 solid nonsabsorbent insulatina` material and the separators and binders being interlocked with the distance pieces, the Whole forming a unit coil. c

Signed at London, England, this 20th day of January, 1922.V Y

' JAN ROOTHAAN. 

